Figure 2.

SAMHD1-mediated suppression of SeV infection–induced NF-κB activation and IFN-I induction requires its dNTPase activity in differentiated U937 cells. Differentiated U937 cells stably expressing WT SAMHD1 or HD/RN were infected with SeV at the m.o.i. of 10 for 6 h or mock infected. A, Cell lysates were used to test the expression levels of HA-tagged SAMHD1, total and phosphorylated IkBα, and GAPDH by SDS-PAGE. Dimerization of IRF7 was also tested in native PAGE separately. B and C, dNTPase activity of SAMHD1 is needed for suppressing NF-κB activation and IFN-I induction after SeV infection. Relative mRNA levels of TNF-α (B), IFN-α (C), and IFN-β (C) in cell pellets were measured by RT-PCR. D, IFN-β protein levels in the supernatants were tested after 24 h SeV infection. Results are shown as mean ± S.D. Statistical significance was determined by unpaired Student's t test; *, p < 0.05; **, p < 0.01 compared with vector controls. The results are representative of three independent experiments.